Tubing injector

ABSTRACT

A tubing injector for injecting tubing ( 4 ) into a pipeline or bore or the like comprises: an annular piston for moving the tubing ( 4 ); a collet for gripping the tubing on movement of the piston in an injecting direction, the collet ( 14 ) and the tubing being movable with the piston, and the collet being releasable from the tubing ( 4 ) on movement of the piston in another direction, and a ratchet collet for preventing the tubing from being ejected.

FIELD OF THE INVENTION

The present invention relates to a tubing injector, in particular aninjector for conveying coiled tubing or the like through a bore or othersuch opening.

BACKGROUND OF THE INVENTION

The oil and gas industry makes wide use of coiled tubing, in for examplewell intervention, coiled tubing drilling and pipeline maintenance. Inorder to inject tubing into a well, and also pull it therefrom, a tubinginjector must be provided on the surface. Conventional tubing injectorsare large and heavy, and also relatively complex. The main reason forthis is the very large pulling and injection forces required for thesuccessful deployment of the tubing.

In order to repair sub-sea pipelines, coiled tubing can be injectedthrough a hot tap while the pipeline is under a pressure of typically100–200 bar. This tubing is used to deploy inflatable stoppers or plugsto isolate particular pipeline sections. By doing this, repairs can bemade to the isolated sections without having to close down the entirepipeline, which as will be appreciated would incur considerable costsand cause considerable inconvenience.

A problem with existing injectors is that injection and indeed ejectionof coiled tubing can be difficult to control when there is a pressuredifferential between the pipeline and the exterior of the tool.Typically, large injection and pulling forces are needed, which as notedabove, means that equipment tends to be large and heavy. This can causeproblems, because pipeline repairs often need to be done at shortnotice, anywhere in the world and deployed from a variety of supportvessels. The need for rapid deployment means that it is important thattubing injectors are compact and can be easily broken down into smallparts for transportation by conventional aircraft and/or helicopter. Inaddition, the injectors have to be simple enough to be reliable andeasily stripped down and serviced in the field.

An object of at least one embodiment of the invention is to provide asimple and compact coiled tubing injector.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a tubing injectorfor injecting tubing into a pipeline or bore or the like, the injectorcomprising:

-   -   translation means for moving the tubing;    -   gripping means for gripping the tubing on movement of the        translation means in an injecting direction, the gripping means        and the tubing being movable with the translation means, and the        gripping means being releasable from the tubing on movement of        the translation means in another direction, and    -   retaining means for preventing the tubing from being ejected.

Having the gripping means in engagement with the tubing and movable withthe translation means causes the tubing to be fed or injected into thepipeline. Return movement of the tubing in an ejection direction isavoided when the gripping means is released by the action of theretaining means.

The gripping means may be annular, for example a collar, preferably acollet. The collet may be spring energised and/or dual action. Means maybe provided for releasing the gripping means, for example a piston, inparticular a hydraulically actuated piston.

The retaining means may be operable to retain the tubing when theretaining means are in their steady state or normal condition. Movementof the tubing in an injection direction may release the retaining means.The retaining means may be mechanically actuatable, preferablyautomatically by reverse movement of the tubing. The retaining means maybe spring actuated. The retaining means are preferably providedinternally of the tool. The retaining means may comprise a ratchet. Theretaining means may comprise a collet, for example a ratchet collet. Theretaining means may be releasable. The retaining means may be releasableby the action of a piston, for example a hydraulically actuated piston.

The translation means may be annular and extend around the tubing inuse. The translation means may be a piston, preferably an annularpiston. Use of an annular piston and an annular gripping means, allowsthe injector to be generally elongate, extending along an axis of thetubing. This helps reduce the overall bulk and size of the injector.

According to another aspect of the invention, there is provided a methodof injecting tubing into a pipeline or bore or the like, the methodcomprising:

-   -   gripping the tubing using gripping means;    -   moving the gripping means and the tubing in an injection        direction;    -   retaining the tubing in a relatively fixed position using        retaining means disposed internally of the tool; and    -   releasing the gripping means.

By retaining the tubing using the retaining means the gripping means canbe released and moved, without any danger of the tubing being ejecteddue to internal pressure in the pipeline.

The steps of retaining and releasing may be effected automatically onmovement of the gripping means.

According to still another aspect of the invention, there is provided amethod of ejecting tubing from a pipeline or the like, the methodcomprising:

-   -   retaining the tubing in a relatively fixed position using        retaining means disposed internally of the tool;    -   gripping the tubing using gripping means;    -   releasing the retaining means;    -   moving the gripping means towards an upper end of the injector        to eject the tubing;    -   re-applying the retaining means to prevent further ejection;    -   releasing the gripping means;    -   moving the gripping means to an ejection position towards a        lower end of the injector;    -   gripping the tubing using the gripping means;    -   releasing the retaining means, and    -   moving the gripping means towards the upper end of the injector.

By carefully controlling the action of the gripping and the retainingmeans, it can be ensured that the tubing is at all times held securelywithin the tool and can be ejected in a controlled manner. This can bedone even when there is a significant pressure differential, which wouldotherwise tend to eject the tubing in an uncontrolled and potentiallydangerous manner.

According to yet another aspect of the invention, there is provided atubing injector for injecting tubing into a pipeline or bore or thelike, the injector comprising a plurality of detachable units, whichunits are co-axially connectable to define an elongate housing, throughwhich tubing can pass. The units may be adapted to be screw fittedtogether.

By providing co-axially detachable/connectable units, the injector canbe disassembled and transported easily.

One of the units may include a translation means for moving the tubing.Another of the units may include gripping means for gripping the tubingon movement of the translation means in an injecting direction, thegripping means and the tubing being movable with the translation means,and the gripping means being releasable from the tubing on movement ofthe translation means in another direction. The gripping means may be acollet. Yet another of the units may include retaining means forpreventing the tubing from moving in an ejection direction. Theretaining means may be a collet, preferably a ratchet collet.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the invention will now be described, by way ofexample only, with reference to the accompanying drawings, in which.

FIG. 1 is partially sectioned view of a tubing injector, with a tubeshown in situ, and

FIG. 2 is a section on the line A—A of the injector of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

The injector of FIGS. 1 and 2 has an elongate tool housing 10 along alongitudinal axis of which lie the parts of the injector, these partsbeing coaxial and arranged to define a central through passage forcoiled tubing 4. For the purposes of this description, the lower end 6of the injector is defined as the end that is closest to the pipeline orbore into which the tubing 4 is to be injected, the upper end 8 beingthe other end.

At the upper end 8 of the tool housing 10 is a hydraulically actuatableannular release piston 12 that is operable to release a double actingshuttle collet 14 that is energisable by a spring 15. Included in theshuttle collet 14 are collet members 16 that have two annular surfaces,one of which 18 is tapered towards the upper end 8 of the tool, theother 20 being tapered towards the lower end 6 of the tool, as shown inFIG. 2. These collet members 16 are movable towards the upper end of thetool within similarly shaped cavities defined in the tool housing 10. Ina normal condition, the shuttle collet members 16 are biased by theenergising spring 15 against the cavity walls and inwardly towards thecentral axis of the tool, thereby to grip any tubing 4 that is in situ.However, movement of the shuttle collet towards the upper end 8 of theinjector releases the collet members 16 from their gripping engagement.

Shuttle collet 14 is a double acting collet and can be released by theapplication of hydraulic pressure to the shuttle collet release piston12. The release piston 12 can also be used to cause the shuttle collet14 to act in the opposite direction, i.e. pull rather than push. This isdone by over-riding the energising spring.

Connected to shuttle collet 14 is an annular push-pull (double-acting)or stroke piston 20. At a lower end of the piston is a coiled tubingguide 22 for guiding tubing towards a lower part of the tool and toprevent tubing buckling. The piston 20 is adapted to slide over thisguide 22. In use, downwards movement of the piston 20, towards the lowerend 6 of the tool, causes the shuttle collet 14 to move. Because theshuttle collet members 16 grip the tubing 4 that is within the injector,this movement of the piston 20 causes both the shuttle collet 14 and thetubing 4 to move in a downwards direction, so that the tubing 4 isinjected.

At the lower end 6 of the tool is a single acting collet 24, sometimesreferred to as a ratchet collet, for gripping the tubing. This isenergised by a spring 28. Included in the ratchet collet 24 are annularratchet collet members 26 that are tapered towards the upper end 8 ofthe tool, as shown in FIG. 2. The ratchet members 26 are movable withinsimilarly shaped cavities in the tool housing. The ratchet colletmembers 26 and housing are shaped so that in normal condition they areforced by the action of the spring 28 against the cavity walls andinwardly towards the axis of the tool, thereby to grip the tubing 4.However, movement of the tubing 4 towards the lower end 6 of theinjector releases the collet members 26 from their gripping engagementto allow the tubing 4 to be injected. In the event that the tubing isstationary or indeed moves towards the upper end of the injector, thespring 28 biases the collet members 26 against the tubing 4, therebypreventing the tubing from moving out of the injector.

As will be appreciated, the ratchet collet 24 is uni-directional in thesense that it does not affect movement of tubing towards the lower end 6of the tool, but acts to prevent the tubing 4 moving towards the upperend 8. The ratchet collet 24 is spring 28 energised and can be releasedby the action of an annular hydraulic release piston 30, which piston 30is provided between the tubing guide 22 and the ratchet collet 24.However, in the event that the unit is being used in a reverse pressureapplication, such as in very deep water where the ambient pressureoutside the pipeline exceeds the internal pipeline pressure, theorientations of the ratchet collet 24 and the shuttle collet 14 may bereversed.

In order to simplify assembly of the tool of FIGS. 1 and 2, the housing10 is preferably divided into several detachable units. For example, theshuttle collet 14 and the shuttle collet release piston 12 could beprovided in an elongate unit 32 that is releasably attachable to thepiston 20. Likewise, the piston 20 may be housed in a unit 34 that isreleasably attachable to another unit 36 that includes the ratchetcollet 24 and the ratchet collet release piston 30. The units 32,34 and36 may be attachable in any suitable way, for example using a simplescrew fitting arrangement. By providing detachable units, the injectorcan be readily disassembled for transportation, for example by air, andequally easily assembled as and when desired.

In normal operation of the injector of FIGS. 1 and 2, tubing 4, forexample composite coil tubing, is inserted through the tool andinjection is caused by the dual action of the shuttle collet 14 and thestroke piston 20. While injecting, no hydraulic pressure is provided toeither the shuttle collet release piston 12 or the rachet collet releasepiston 30. Movement of the piston 20 downwards towards the lower end 6of the tool causes the shuttle collet 14, which is in grippingengagement with the tubing 4, to move. Continued movement downwardscauses both the shuttle collet 14 and the tubing 4 to move through thetool, thereby injecting the tubing into the pipe.

Once the piston 20 is fully extended, it begins its return stroke. Atthis stage the tubing 4 is still gripped by the shuttle collet 14.However, movement of the tubing 4 in the reverse direction towards theupper end 8 of the tool causes the ratchet collet 24 to move into itssteady state gripping position. Subsequent movement of the piston 20,and so the tubing 4, in the reverse direction causes the ratchet collet24 to increase its grip on the tubing 4 at the same time as releasingthe shuttle collet 14. In this way, the piston 20 and shuttle collet 14can be returned to the starting position, whilst rearwards movement ofthe tubing 4 is prevented by the ratchet collet 24.

When removing the coiled tubing 4 from the pipeline, it is necessary tocontrol the rate at which the tubing 4 may be ejected by the pressuredifferential within the pipeline and the ambient pressure outside theline. This pressure is contained by a conventional stuffing box (notshown).

In this mode, during ejection, the ratchet collet 24 is released, usingrelease piston 30, when the piston 20 is in the downwards position withthe shuttle collet 14 gripping the coiled tubing 4. The tubing 4 canthen be allowed to eject itself by controlling the fluid release fromthe pressure side of the stroke piston 20 until it has returned to itsupwards position. At this stage, or just before it, the hydraulicpressure is released from the ratchet collet release piston 30 causingthe ratchet collet 24 to grip the coiled tubing 4, preventing furtherejection.

To return the stroke piston 20 to the downward position, hydraulicpressure is applied to the shuttle collet release piston 12. Thisreleases the grip of the shuttle collet 14 and allows the stroke piston20 to move down the now stationary coiled tubing 4. Hydraulic pressureto the shuttle collet release piston 12 is removed before the strokepiston 20 reaches its full downward position, allowing the shuttlecollet 14 to grip the tubing 4 and take the load off the ratchet collet24 ready for the next return stroke of the system. By repeating thissequence, the tubing can be removed from the pipeline in a controlledmanner.

Control of the tubing injection operation is achieved using a hydrauliccontrol system (not shown). This system is configured to prevent thepossibility of hydraulic release pressure being applied to both of theratchet collet 24 and the shuttle collet 14 at the same time, and thusprovides for failsafe operation. The control system also ensures thatthe ratchet collet 24 can only be hydraulically released when the piston20 is in the downwards position with sufficient hydraulic activationpressure behind it to control the ejection force of the coiled tubing 4being removed from the pipeline.

In the event that no pressure differential exists between the pipelinebore and ambient outside pressure then the double acting feature of theshuttle collet can be used to pull the tubing from the pipeline simplyby changing the hydraulic sequence of operations.

The injector in which the invention is embodied is simple and compact.By using annular collets, gripping can be maximised and damage to thetubing minimised. The injector can also be manufactured at relativelylow cost and requires low maintenance. Hence, it can be serviced andoperated at remote locations around the world. Furthermore, it can bemade of a low weight and size for deployment subsea.

It will be clear to those skilled in the art that the above-describedembodiment is merely exemplary of the present invention, and thatvarious modifications and improvements may be made thereto withoutdeparting from the scope of the invention. For example, as noted above,a modified unit in accordance with a further embodiment of the inventionmay be used in a reverse pressure application, such as in very deepwater (1,000 to 2,000 metres) where the ambient pressure outside thepipeline exceeds the internal pipeline pressure. For such an applicationthe orientations of the ratchet collet 24 and the shuttle collet 14 arereversed, to allow the unit to control the injection of the coiledtubing 4 in the presence of a pressure differential tending to push thetubing 4 into the pipeline. Conversely, the unit will be operated todraw the tubing 4 from the pipeline during ejection, against thepressure force tending to draw the tubing 4 into the pipeline.

1. A tubing injector for injecting tubing into a pipeline or bore or the like, the injector comprising: a translation device for translating the tubing; a gripping device movable by the translation device, the gripping device being operable to grip the tubing during movement of the translation device in an injecting direction, thereby to inject the tubing, and to be released from the tubing on movement of the translation device in another direction, wherein the gripping device is located at least partially within the translation device; and a retaining device for preventing the tubing from being ejected.
 2. An injector as claimed in claim 1, wherein the gripping device is operable to grip the tubing when in a normal or steady state condition.
 3. An injector as claimed in claim 1, wherein the gripping device is adapted so that movement of the translation device in the said other direction moves the gripping device to a configuration in which the tubing is released therefrom.
 4. An injector as claimed in claim 1, wherein the gripping device is a collet.
 5. An injector as claimed in claim 1, wherein the collet is spring-energized.
 6. An injector as claimed in claim 4, wherein the collet is dual action.
 7. An injector as claimed in claim 1, wherein a member is provided for releasing the gripping device.
 8. An injector as claimed in claim 7, wherein the member for releasing comprises a release piston.
 9. An injector as claimed in claim 8, wherein the release piston is a hydraulically actuated piston.
 10. An injector as claimed in claim 1, wherein the retaining device is operable to retain the tubing when the tubing is not moving in the iniecting direction.
 11. An injector as claimed in claim 10, wherein the retaining device is operable to be released on movement of the tubing in the injection direction.
 12. An injector as claimed in claim 11, wherein the retaining device is automatically released on movement of the tubing in the injection direction.
 13. An injector as claimed in claim 1, wherein the retaining device is mechanically actuatable.
 14. An injector as claimed in claim 1, wherein the retaining device is spring actuated.
 15. An injector as claimed in claim 1, wherein the retaining device is provided internally of the injector.
 16. An injector as claimed in claim 1, wherein the retaining device comprises a ratchet.
 17. An injector as claimed in claim 1, wherein the retaining device comprises a collet.
 18. An injector as claimed in claim 17, wherein the retaining device comprises a ratchet collet.
 19. An injector as claimed in claim 1, wherein a device for releasing the retaining device is provided.
 20. An injector as claimed in claim 19, wherein the device for releasing the retaining device comprises a piston.
 21. An injector as claimed in claim 20, wherein the device for releasing the retaining device comprises a hydraulically actuated piston.
 22. An injector as claimed in claim 1, wherein the translation device is annular and adapted to extend around the tubing.
 23. The injector of claim 1, wherein the translation device is a piston and cylinder assembly.
 24. The injector of claim 23, wherein the gripping device is a collet.
 25. The injector of claim 24, wherein the collet is spring energized.
 26. A method of injecting tubing into a pipeline or bore or the like, the method comprising: gripping the tubing using a gripping device; moving the gripping device and the tubing in an injection direction with a translation device, wherein the gripping device is located at least partially within the translation device; retaining the tubing in a relatively fixed position using a retaining device; and releasing the gripping device.
 27. The method of claim 26, wherein the translation device is a piston and cylinder assembly.
 28. The injector of claim 27, wherein the gripping device is a collet.
 29. A method of ejecting tubing from a pipeline or the like, the method comprising: retaining the tubing in a relatively fixed position using a retaining device; gripping the tubing using a gripping device; releasing the retaining device; moving the gripping device towards an upper end of the injector to eject the tubing with a piston and cylinder assembly, wherein the gripping device is located at least partially within the piston and cylinder assembly; re-applying the retaining device to prevent further ejection; releasing the gripping device; moving the gripping device to a position towards a lower end of the injector; gripping the tubing using the gripping device; releasing the retaining device; and moving the gripping device towards the upper end of the injector.
 30. A tubing injector for injecting tubing into a pipeline or bore or the like, the injector comprising a plurality of detachable units, the units being co-axially connectable to define an elongate housing; through which tubing can pass, wherein at least one of the units includes: a collet movable by a translation device; and a gripping device being operable to grip the tubing during movement of the translation device in an injecting direction, thereby to inject the tubing, and to be released from the tubing on movement of the translation device in another direction.
 31. An injector as claimed in claim 30, wherein the units are adapted to be screw fitted together.
 32. An injector as claimed in claim 30, wherein yet another of the units includes a retaining device for preventing the tubing from moving in a reverse or ejection direction.
 33. An injector as claimed in claim 32, wherein the retaining device comprises a collet.
 34. An injector as claimed in claim 33, wherein the retaining device comprises a ratchet collet.
 35. A tubing injector for injecting tubing into a pipeline or bore or the like, the injector comprising: a translation device for the tubing; a gripping device movable by the translation device, the gripping device being operable to grip the tubing during movement of the translation device in an injecting direction, and to be released from the tubing on movement of the translation device in another direction; and a retaining device for preventing the tubing from being ejected, wherein the retaining device is provided internally of the injector. 